Matrixing apparatus for a color television system



Sept. 5, 1967 D. RIcI-IMAN 3,340,355

MATRIXING APPARATUS FOR A COLOR-TELEVISION SYSTEM Filed June 5, 1953 3Sheets-Sheet 2 3l6 T g; I26 60 1 LOW-PASS PHASE 0 It FILTER INVERTER 6oGHROMATIClTY- NET WORK I I o SIGNAL O-LSMC. V o i I ODETECTOR a 1- I 6II II o I 1 g g a POTENTIAL NETWORK SOURCE o-sooxc. 0 g c 0 I I I I l II I l D. RICHMAN Sept. 5, 1967 MATRIXING APPARATUS FOR ACOLOR-TELEVISION SYSTEM 3 Sheets-Sheet 3 Filed June 5, 1953 O BAND- PASSFILTER NETWORK SIS; f

United States Patent 3,340,355 MATRIXING APPARATUS FOR A COLOR-TELEVISION SYSTEM Donald Richman, Flushing, N.Y., assignor t0 HazeltineResearch, Inc., Chicago, 111., a corporation of Illinois Filed June 5,1953, Ser. No. 359,734 16 Claims. (Cl. 178-5.4)

General The present invention is directed to matrixing apparatus for acolor-television system and, particularly, to such apparatus incolor-television receivers for developing from a pair of signalsindividually representative of different components of the color of atelevised image signals representative of other different components ofthe color of the aforesaid image.

In a form of color-television system more completely described in anarticle in Electronics for February 1952 entitled, Principles of NTSCCompatible Color Television, at pages 8895, inclusive, information representative of a scene in color being televised is utilized to develop atthe transmitter two substantially simultaneous signals, one of which isprimarily representative of the luminance and the other representativeof the chromaticity of the image. To develop the latter signals, thescene being televised is viewed by one or more television cameras todevelop color signals individually representative of such primary colorsas green, red, and blue of the scene and these signals are combined in amanner more fully described in the aforesaid article to develop a signalwhich primarily represents all of the luminance or. brightnessinformation relating to the televised scene. Additionally, these colorsignals or signals representative thereof are individually applied asmodulation signals to a subcarrier wave signal developed at thetransmitter, effectively to modulate the latter signal at predeterminedphase points thereof to develop the signal representative of thechromaticity of the scene being televised. Conventionally, the modulatedsubcarrier wave signal or chromaticity signal has a predeterminedfrequency less than the highest video frequency, for example, afrequency of approximately 3.6 megacycles, and has amplitude and phasecharacteristics related to the saturation and hue of the color beingtransmitted. In the specific form of such system, as described in theaforementioned article, the three color signals are initially modifiedto become three color-difference signals, in other words, to becomesignals such that when they are individually added in a receiver to theluminance signal, color signals will be developed. Such color-differencesignals are usually, but not necessarily, limited in band width to lessthan 2 megacycles and dilferent ones thereof may have different bandWidths. The three color-difference signals are combined to form twocomposite signals which are utilized to modulate the subcarrier wavesignal at quadrature-phase points thereof. In one embodiment of suchsystem, which will be considered more fully hereinafter, the phase axesof such quadrature signals do not coincide with any of the three phaseaxes of the color-difference signals as they inherently occur asmodulation components of the subcarrier wave signal. It has becomeconventional to designate the quadrature signals as I and Q signals andthe color-difference signals as G-Y, R-Y, and BY signals, the latterthree signals representing respectively the green, red, and blue colorsof the image. For reasons 3,340,355 Patented Sept. 5, 1967 too whichneed not be considered more fully herein, the quadrature signal I isusually proportioned to have a band width of approximately 1.3megacycles, while the signal Q has a band width of approximately 0.4megacycle. After the modulated subcarrier wave signal including the Iand Q signals as modulation components has been developed, the latterwave signal is combined with the luminance signal in an interlacedmanner to form in a pass band common to both signals a resultant composite video-frequency signal which is transmitted in a conventionalmanner.

A receiver in such a television system intercepts the transmitted signaland initially derives therefrom the chromaticity signal and theluminance or brightness signal. The quadrature-modulation components ofthe chromaticity signal, specifically, the I and Q signals, are derivedby a detection means which is designed to operate in synchronism and inproper phase relation with the subcarrier wave-signal modulating meansat the transmitter. In view of the lack of coincidence between thequadrature-phase axes of the I and Q signals and the phase axes of thethree color-difference signals as modulation signals of the subcarrierwave signal, the detection means further comprises a signal-combiningcircuit for combining components of the derived I and Q signals todevelop the color-difference signals G-Y, R-Y, and B-Y. Thecolor-difference signals, desirably including only chromaticityinformation, and the derived luminance signal are combined to developcolor signals individually representative of the green, red, and blue ofthe televised image. After being effectively combined, these colorsignals are utilized in an image-reproducing apparatus to cause thisapparatus to develop a color reproduction of the televised scene.

In present detection means in color-television receivers for developingcolor-difference signals for utilization in such receivers, detectioncircuits are included for deriving the I and Q signals from themodulated subcarrier wave signal. Since the I and Q signals do not lendthemselves directly to utilization by available image-reproducingapparatus, a matrixing apparatus is utilized to combine components ofthe I and Q signals in different proportions and senses to developcolor-difference signals which may be utilized by such image-reproducingapparatus. Such detection means and particularly the matrixing apparatustherein tends to become complex, cumbersome, and expensive because ofthe multiplicity of circuits included to perform the many variedoperations, especially if such operations are performed as at present ina step-by-step manner.

It is, therefore, an object of the present invention to provide a newand improved matrixing apparatus for a color-television system whichdoes not have the disadvantages and limitations of prior such apparatus.

It is also an object of the invention to provide a new and improvedmatrixing apparatus for a color-television system which includes anexceptionally small number of circuit elements to accomplish itspurpose.

It is a further object of the invention to provide a new and improvedmatrixing apparatus for a color-television system in which the circuitelements thereof perform multiple functions.

In accordance with the .present invention, a matrixing apparatus isincluded in a color-television system for developing from a pair ofsignals individually representative of different components of the colorof a televised image signals representative of other differentcomponents of the color of the image. The matrixing apparatus comprisesa pair of signal sources for individually supplying different ones ofthe aforesaid pair of signals, these sources including individual pairsof output terminals having a terminal common to the aforesaid pairs ofoutput terminals. The matrixing apparatus also comprises an impedancenetwork coupled to the aforesaid sources and including three loadcircuits each having two terminals. One terminal is common to the threeload circuits and the other terminal of one of the load circuits iscoupled to the common output terminal of the aforesaid sources. Theother terminals of the others of the load circuits are individuallycoupled to different ones of the other output terminals for causingcurrents representative of both of the supplied signals to flow througheach of the load circuits. The impedances of the load circuits are soproportioned relative to each other that the currents fiowing throughdifferent ones thereof individually represent the aforesaid otherdifferent components of the color.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings, and itsscope Will be pointed out in the appended claims.

Referring now to the drawings:

FIG. 1 is a schematic diagram of a color-television receiver including amatrixing apparatus in accordance with the present invention;

FIG. 2a is a graph useful in explaining the operation of the matrixingapparatus of FIG. 1;

FIG. 2b is a circuit diagram useful in explaining the operation of thematrixing apparatus of FIG. 1;

FIG. 3 is a schematic diagram of a modified form of the matrixingapparatus of FIG. 1;

FIG. 4 is a circuit diagram of a modified form of a portion of thematrixing apparatus of FIG. 3, and

FIG. 5 is a schematic diagram of a modified form of the matrixingapparatus of FIG. 1.

General description of receiver of FIG. 1

Referring now to FIG. 1 of the drawings, there is rep resented acolor-television receiver of the superheterodyne type such as may beused in a color-television system of the type previously discussedherein and in the aforesaid Electronics article. It is preferable,though not essential, that properly developed luminance and chromaticitysignals, which will be considered more fully herein-after, are utilizedin such television system. The receiver includes a carrier-frequencytranslator having an input circuit coupled to an antenna system 11, 11.It will be understood that the unit 10 may include in a conventionalmanner one or more stages of wave-signal amplification, anoscillator-modulator, and one or more stages of intermediate-frequencyamplification, if such are desired. Coupled in cascade with the outputcircuit of the unit 10, in the order named, are a detector andautomatic-gain-control (AGC) supply 12, a video-frequency amplifier 13having 'a pass band preferably of 0-4.3 megacycles, and animage-reproducing device 14 having a cathode input circuit to which theoutput circuit of the amplifier 13 is connected. The amplifier 13 is anamplifier for the brightness or luminance signal and the output circuitthereof is additionally connected through a pair of terminals 21, 21 toa direct-current restorer circuit in a unit 16 in accordance with thepresent invention and to be considered more fully hereinafter. Thedevice 14 may, for example, comprise a single cathode-ray tube having aplurality of cathodes and a plurality of control electrodes, differentpairs of the cathodes and the control electrodes being individuallyresponsive to different col-or signals, as will be explained more fullyhereinafter, and including an arrangement for directing the beamsemitted from the cathodes individually onto diiferent phosphors fordeveloping different primary colors. Such a tube is more fully describedin an article entitled General Description of Receivers for theDot-Sequential Color Television System Which Employ Direct-ViewTri-Color Kinescopes in the RCA Review for June 1950 at pages 228-232,inclusive. It should be understood that other suitable types ofcolor-television image-reproducing devices may be employed.

An output circuit of the detect-or 12 is coupled through an amplifier15, preferably having a pass band of 2,-4.3 megacycles, and a matrixingapparatus 16, in accordance with the present invention and to bedescribed more fully hereinafter, to the control electrodes of theimage-reproducing device 14. The apparatus 16 has a pair of inputterminals 30, 30 connected to the output circuit of the amplifier 15 andhas a plurality of pairs of output terminals 31, 31, 32, 32, and 33, 33individually connected to different ones of the control-electrodecircuits in the device 14. The amplifier 15 is an amplifier for themodulated subcarrier wave signal and, thus, the chromaticity signalpreviously considered herein.

An output circuit of the detector 12 is also coupled through asynchronizing-signal separator 17 to a line-scanning generator 18 and afield-scanning generator 19, output circuits of the latter units beingcoupled, respectively, to line-deflection and field-deflection windingsof the image-reproducing device 14. An output circuit of the generator18 is also coupled through a pair of terminals 20, 20 to the keyeddirect-current restorer circuit in the matrixing apparatus 16.

An output circuit of the synchronizing-signal separator 17 is coupledthrough an automatic-frequency-control system 22 to a signal generator23, preferably having a frequency of approximately 3.6 megacycles. Theoutput circuit of the generator 23 is coupled through a phase shifter 25and a pair of terminals 26, 26 to an input circuit of the matrixingapparatus 16, and the output circuit of the generator 23 is also coupledthrough a pair of terminals 24, 24 to another input circuit of theapparatus 16.

The AGC supply of the unit 12 is connected through the conductoridentified as AGC to input terminals of one or more of the stages in theunit 10 to control the gains of such stages to maintain the signal inputto the detector 12 within a relatively narrow range for a wide range ofreceived signal intensities. A sound-signal reproducing unit 27 is alsoconnected to an output circuit of the unit 10 and it may include stagesof intermediatefrequency amplification, a sound-signal detector, stagesof I audio-frequency amplification, and a sound-reproducing device.

It will be understood that the various units thus far described, withthe exception of the matrixing apparatus 16, may be of any conventionalconstruction and design, the details of such units being well known inthe art and requiring no further description.

General operation of receiver of FIG. 1

Considering briefly now the operation of the receiver of FIG. 1 as awhole, a desired composite television signal preferably of the constantluminance type is intercepted by the antenna system 11, 11, is selected,amplified, converted to an intermediate frequency, and further amplifiedin the unit 10, and the video-frequency modulation components thereofare derived in the detector 12. These video-frequency modulationcomponents comprise synchronizing components, the aforementionedmodulated wave signal or chromaticity signal, and a luminance orbrightness signal. The luminance or brightness signal is furtheramplified in the amplifier 13 applied to the cathodes of theimage-reproducing device 14 and through the as well as a color burstsignal for synchronizing the operation of the color-signal derivingapparatus in the unit 16 are separated from the video-frequencycomponents and from each other in the synchronizing signal separator 17.The line-frequency and field-frequency synchronizing components areapplied, respectively, to the units 18 and 19 to synchronize theoperation of these generators with the operation of related units at thetransmitter. These generators supply signals of saw-tooth wave formwhich are properly synchronized with respect to the transmitted signaland are applied to the line-deflection and field-deflection windings inthe device 14 to effect a rectilinear scanning of the image screen inthe device 14. The color burst signal which is substantially a fewcycles of an unmodulated portion of the subcarrier wave signal having adesired reference phase is applied to the automatic-frequency-controlsystem 22 to control the frequency and phase of the signal developed inthe signal generator 23. The unmodulated signal developed in thegenerator 23 is applied substantially without phase delay throughterminals 24, 24 and with substantially 90 phase delay through the unit25 and the terminals 26, 26' to the color signal deriving apparatus inthe unit 16.

The modulated subcarrier wave signal is amplified in the unit 15 andapplied through the terminals 30, 30 to the matrixing apparatus 16. Theunit 16, in a manner to be explained more fully hereinafter, initiallyeffects the derivation of the quadrature components of the subcarrierwave signal, specifically, the I and Q signals, and from these developsGY, R-Y, and B-Y color-difference signals. The latter color-differencesignals are individually applied through different pairs of theterminals 31, 31, 32, 32, and 33, 33 to different ones of the controlelectrodes of the image-reproducing device 14. The luminance signalapplied to the cathodes of this device and each of the color-differencesignals effectively combine in the device 14 to develop color signals G,R, and B and individually control the intensities of different beams inthe device 14. This intensity modulation of the cathode beams togetherwith their alignment and the resultant excitation of different colorphosphors on the imagesereen of the device 14 is effective to cause acolor image to be reproduced on such screen.

The automatic-gain-control (AGC) signal developed in the unit 12 iseffective to control the amplification of one or more of the stages inthe unit 10, thereby to maintain the signal input to the detector 12 andto the soundreproducing apparatus 27 within a relatively narrow rangefor a wide range of received signal intensities. The sound-signalmodulated wave signal having been selected and amplified in the unit isapplied to the sound-reproducing apparatus 27. Therein it is amplifiedand detected to derive the sound-signal modulation components which maybe further amplified and then reproduced in the reproducing device ofthe unit 27.

Description of malrz'xing apparatus of FIG. 1

Referring now to the matrixing apparatus 16 of FIG. 1, as will be madeclear hereinafter, the purpose of the apparatus 16 in a color-televisionsystem is to develop from a pair of signals, specifically, frommodulation signals I and Q which are composite signals individuallycomprising in predetermined proportions a plurality of signalsindividually representative of different primary colors of a televisedimage, signals representative of other different components of the colorof the image, specifically, color-difference signals such as GY, R-Y,and BY. The apparatus 16 comprises a pair of signal sources forindividually supplying different ones of the I and Q signals, thesesources including individual pairs of output terminals having a terminalcommon to the pairs. More specifically, these sources of the I and Qsignals comprise means for supplying a modulated wave signal, having theI and Q signals as modulation components thereof, and a pair of balanceddetector circuits for deriving from the subcarrier wave signal the I andQ modulation components thereof so that the derived components havedifferent magnitudes and polarities. The means for supplying themodulated wave signal comprises a supply circuit, specifically, atransformer 46 and the pair of terminals 30, 30, the primary of thetransformer being coupled through the terminals 30, 30 to the outputcircuit of the amplifier 15. The supply means also includes thesecondary winding of the transformer 46 which has two pairs ofterminals, specifically, pairs 47, 47 and 48, 48 and a terminal 49intermediate both of these pairs for supplying the modulated wave signalat different magnitudes. For the purpose of obtaining such magnitudes,for reasons which Will be explained more fully hereinafter, the turns ofthe secondary winding between the terminals 47, 47 and be tween theterminals 48, 48 are in the ratio of 4.34:3.73 when the gains for the Iand Q signals are substantially equal in the channels prior to the pairof terminals 48, 48.

One of the balanced detectors of the aforementioned signal sourcescomprises a pair of electron-discharge devices, specifically, diodes 40and 41 connected in series through the terminals 47, 47 with thesecondary winding of the transformer 46, the anode of the diode 41 beingconnected to the cathode of the diode 40 and also coupled through atransformer 42 and the pair of terminals 26, 26 to the output circuit ofthe phase shifter 25. The diodes 40 and 41 are so poled as to conductcurrent in one sense, specifically, from the upper terminal 47 to thelower terminal 47 for deriving the modulation component Q with anegative polarity. It will be understood that when the term polarity isused herein with respect to signals such as I and Q which may be otherthan unidirectional in potential, it is meant that the instantaneousrelative polarities of such signals are either in the same sense and,thus, both positive or both negative or are in opposite senses and,thus, one negative and the other positive.

The other balanced detector comprises a similar pair of diodes 43 and 44connected in series with a portion of the secondary winding of thetransformer 46 through the terminals 48, 48 and coupled through atransformer 45 and the pair of terminals 24, 24 to the output circuit ofthe generator 23. The diodes 43 and 44 are effectively in parallel withthe diodes 40 and 41 and are so poled as to conduct in a sense oppositethe sense of conduction of the diodes 40 and 41, specifically, from thelower terminal 48 to the upper terminal 48 for deriving the modulationcomponent I with a positive polarity. The detector including the diodes40, 41 includes a pair of output terminals 49, 50, the terminal 50 beingat the end of the secondary winding of the transformer 42 remote fromthe connection of such winding to the diodes 40 and 41. The detectorincluding the diodes 43 and 44 also includes a pair of output terminalsone of which is the terminal 49 and the other of which is a terminal 51at the end of the secondary winding of the transformer 45 remote fromthe coupling of such winding to the diodes 43 and 44.

The matrixing apparatus also comprises an impedance network,specifically, a network 52 coupled to the aforesaid sources andincluding three load circuits each having two terminals, one of which isa common terminal 54 with the other terminal of one of the load circuitscoupled to the common output terminal 49 and with the other terminals ofthe others of the load circuits individually coupled to the differentones of the other output terminals. More specifically, the impedancenetwork 52 comprises three load circuits 53g, 53b, and 53r having pairsof terminals 50, 54, 49, 54, and 51, 54, respectively. Each of the loadcircuits comprises a series circuit of an inductor and a resistor inparallel with a condenser, the inductor and condenser comprising afilter circuit, preferably, a low-impedance shunt circuit through thecondenser thereof for signals having frequencies higher than the highestfrequency of the derived modulation signal, for example, higher than 1.5megacycles and,

specifically, for the subcarr'ier wave signal. The resistor in each ofthe load circuits comprises a substantial portion of a high-impedancecircuit, more specifically, being the load resistor for the derivedmodulation components and has a terminal intermediate the end terminalsthereof. The other parameters of such high-impedance circuits areimpedances due to stray capacitance and inductance and to the inherentimpedances of the physical inductors and capacitors in each loadcircuit. The resistors for the circuits 53g, 53b, and 531- are 55g, 55b,and 551', respectively. As will be explained more fully hereinafter, thetotal impedances of the load circuits and the impedances of thefractional portions of the resistors 55g, 55]), and 55r at theintermediate terminals as well as the magnitudes and senses orpolarities of the signals supplied by the balanced detectors are soproportioned relative to each other that the currents flowing throughdifferent ones of the load circuits individually represent differentdesired color-difference signals. Voltages representative of differentones of the color-difference signals are individually developed atdifferent ones of the intermediate terminals. The intermediate terminalsof the resistors 55g, 55b, and 55r are individually connected throughdifferent pairs of the terminals 31, 31, 32, 32, and 33, 33,respectively to different control electrodes in the image-reproducingdevice 14. The common terminal 54 is connected through a condenser 29 tochassis-ground for signals having frequencies higher than the highestfrequency of the derived modulation signal, for example, for signalshaving frequencies higher than 1.5 megacycles.

The impedance network may also include, if directcurrent restoration isdesired, a direct-current restorer circuit 56 having a portion thereofcoupled between the terminal 54 and chassis-ground. Otherwise, theterminal 54 may be connected to chassis-ground or to a source of otherdesired potential level. If a direct-current restorer such as the unit56 is utilized, it comprises a triode 57, the cathode circuit of whichincludes a time-constant circuit 58 having a time constant substantiallylonger than the period of a line of scan. The controlelectrode circuitof the tube 57 is coupled through the pair of terminals 21, 21 to theoutput circuit of the amplifier 13 while the anode circuit of the tube57 is coupled through the transformer 59 and a pair of terminals 20, 20to an output circuit of the line-scanning generator 18. A fractionalportion of the resistor in the time-constant circuit 58 is connectedthrough an intermediate terminal on the resistor to the terminal 54.

Operation of matrixing apparatus of FIG. 1

Prior to considering the details of operation of the matrixing apparatus16 of FIG. 1, it will be helpful to consider generally the manner ofoperation of such apparatus to develop the desired G-Y, B-Y, and RYcolordifference signals individually for application to different onesof the control electrodes in the device 14. In considering such generalexplanation, it will be helpful to refer to the vector diagram of FIG.2a, this diagram representing the relative relations in phase andmagnitude of the modulation components I and Q with respect to eachother and with respect to the desired color-difference signals G-Y, B-Y,and RY as these signals appear as modulation components on the modulatedsubcarrier wave signal applied through the transformer 46 to both of thebalanced detector circuits. The signal derived from the subcarrier wavesignal by the balanced detector including the diodes 40 and 41 is thesignal represented by the vector Q. This derivation is effected in suchbalanced detector by heterodyning the signal developed in the generator23 and which is phase shifted 90 by the unit 25 with the modulatedsubcarrier wave signal applied through the transformer 46 and theterminals 47, 47 to the diodes 40 and 41. The heterodyning of thelocally generated signal and the modulated subcarrier wave signal whenthese signals are in proper phase relation as explained in thepreviously mentioned Electronics article is effective to derive themodulation component at a desired phase angle of the modulatedsubcarrier wave signal, specifically, that component represented by thevector Q. Similarly, at another phase angle the modulation componentrepresented by the vector I is derived by the balanced detectorincluding the diodes 43 and 44. By utilization of the proper turnsratios in the transformer 46, the derived signals I and Q areproportioned to have the relative magnitudes 3.73 and 4.34,respectively, as represented by the lengths of the vectors I and Q. Thereason for such relation in magnitude will be explained more fullyhereinafter. The signal I is positive while the signal Q just mentionedis negative due to the different sensings of the pairs of diodes in thedifferent balanced detector circuits. The signal I is effectivelydeveloped between the output terminals 49, 51 while the signal Q iseffectively developed between the output terminals 49, 50. Thisdevelopment is only an effective development since actually, in view ofthe many purposes of the circuit components in the apparatus 16, complexsignals are developed at these points and an artificial circuit would beneeded to measure the magnitudes of the signals I and Q at these points.

Further examination of the vector diagram of FIG. 2a indicates that thedesired color-difference signals R--Y, BY, and G-Y can be developed fromthe derived signals +1 and Q by combining proper proportions andpolarities of the latter signals. Thus, the signal RY can be developedby combining proper proportions of positive I and positive Q signals,the signal B-Y can be developed by combining proper proportions of apositive Q and a negative I signal, while the signal G-Y can bedeveloped by combining proper proportions of negative I and negative Qsignals. In one type of television system these proportions are definedas follows:

Such proportions are determined by the primary colors employed in thetelevision system and by other factors relating to color fidelity inimage reproduction. It should be understood that the relations definedby Equations l-3, inclusive, are exemplary only and other relations maybe employed equally well without departing from the invention. Theimpedance network 52 and, specifically, the load circuits 53g, 53b, and53r comprise, by mean of the proportioning of the magnitudes and sensesof the signals +1 and Q and of the impedances of the load circuits andof the tapped portions thereof and by means of the current pathsprovided by the connections of such circuits to one another and to thebalanced detector circuits, a matrixing circuit for developing the RY,B-Y, and G-Y signals from the +1 and Q signals. The manner in which theload circuits 53g, 53b, and 531- are proportioned will now be explainedin more detail.

In order to understand the proportioning of the constants of the loadcircuits 53g, 53b, and 531', it is helpful diagrammatically to representthe essential portions of these load circuits and of the sources for the+1 and -Q signals in the manner of FIG. 2b of the drawings. In

FIG. 2b, the generator for developing the --Q signal is represented as KQ where K represents the magnitude of the signal Q. Similarly, thesource of the signal I is represented as K 1. The polarities of +1 and Qare arbitrary and are employed herein because the matrixing apparatus issimpler in design when signals of such polarities are applied to theinput circuits thereof. The load resistors 55g, 55b, and 55r of FIG. 1are represented by the resistors R R and R,, respectively, thefractional portions of these resistors being represented as A R A R andA respectively. The currents flowing from the generators K Q and K 1 arerepresented by the letter i with an initial subscript identifying thegenerator from which the current flows and a second subscriptidentifying the load resistor through which the current is flowing. Thearrows associated with the different current representations indicatethe direction of flow of such currents. For example, the current flowingfrom the generator K Q and through the load resistor R from the highpotential to the ground terminal of such resistor is represented as i Interms of the polarities of the signals I and Q previously mentionedherein to develop the color-difference signals G-Y, R-Y, and B-Y and asdefined by Equations 1-3, inclusive, it should be noted that thedirections of flow of the currents 1' and i through the resistors Rg, Rand R correspond to the required polarities of I and Q to develop thedifferent color-difference signals. Thus, as defined by Equation 1,predetermined amounts of +1 and +Q are required. It should be noted thatthe currents i and i flowing through the load resistor R are in the samesense and may be considered to develop positive components of thesignals I and Q across the resistor R On the other hand, the currentsflowing through the resistor R are also in the same sense but oppositeto the sense of the currents flowing through the resistor R,. Therefore,these may be considered to develop negative components of I and Q asrequired to develop the signal G-Y defined by Equation 3. In a similarrnanner, the currents flowing through the resistor R are in opposingsenses as required to develop the signal B-Y defined by Equation 2. Thedesired magnitudes for the potentials of the signals GY, B-Y, and R-Y,in accordance with the established relationships of such potentials inthe color-television system being utilized, may be developed by properproportioning of the magnitudes of the load resistors R R and R and ofthe fractional portions of these resistors in addition to proportioningthe magnitudes and controlling the senses of the signals I and Q. Thus,in a television system wherein the relationships defined by Equations1-3, inclusive, hold, the proper magnitudes of the signals I and Q fordeveloping the different ones of the color-diiference signals can bedetermined in terms of equations defining the flow of current throughand the potentials developed across the resistors R R and R Thus, thecolor difference signals defined by Equations l-3, inclusive, may befurther defined in terms of current and resistor parameters of thecircuit of FIG. 2b as follows:

The current terms in Equations 4-6, inclusive, by conventional circuitanalysis can be defined in terms of the magnitudes of the signals K Qand K1 and in terms of the total loads for these signals as defined bycombinations of the load resistors R R and R Using such relationshipsand selecting a predetermined parameter for one of the load resistors,for example, the resistor R and assuming that the total resistance R isemployed to develop the signal BY instead of a fractional portionthereof, in other words, assuming A is equal to 1, the following valuesmay be derived for the circuit parameters of a circuit such asrepresented by FIG. 2b:

R =a selected magnitude in ohms R =.79R

Referring again to FIG. 1 and using the relationships just described,the transformer 46, as has been mentioned previously, has such turnsratios in the secondary thereof that the signal Q developed across thesecondary of the transformer 42 and the signal +I developed across thesecondary of the transformer 45 have magnitudes which correspond to therelationships of the factors K and Kj, respectively. The total loadresistance for each of the derived modulation signals in each of theload circuits 53g, 53b, and 53r is defined by the magnitude of thecorresponding one of the resistances R R and R and the magnitude of thefractional portions of the resistors 55g, 55b, and 55r, is as defined bythe terms A A and A respectively. With such proportioning, the signalsdeveloped across the pairs of output terminals 31, 31, 32, 32, and 33,33 are G-Y, B-Y, and RY, respectively, as defined by Equations 1-3,inclusive, above.

The direct-current restorer 56 serves solely to provide direct-currentrestoration for the color-difference signals developed in the loadcircuits 53g, 53b, and 53r. During the blanking period when no videocontent is present in the signal derived in the output circuit of thedetector 12 and translated through the amplifier 13, the tube 57 isgated into conduction by a pulse signal applied from an output circuitof the generator 18 and through the pair of terminals 20, 20 to theanode of the tube 57. Conduction of the tube 57 at this time develops apotential representative of the level of the synchronizing-signal peaksacross the time-constant circuit 58. This potential, due to therelatively long time constant of the circuit 58, remains substantiallyundiminished for at least the period of a line. An appropriate portionof such potential to set black level is tapped from the resistor of thecircuit 58 and utilized to establish black level for the load circuits53g, 53b, and 53r.

Description of matrz'xing apparatus of FIG. 3

Though the matrixing apparatus described with reference to FIG. 1 issimple and is capable of effecting the complex demodulation andmatrixing needed to develop the color-difference signals and utilizes asmall number of circuit components to effect such result, such apparatusmay not provide sufiicient gain for all purposes for the I and Q signalsderived from the subcarrier wave signal, for example, if subcarrier wavesignals of low peak-to-peak amplitude are employed or increased noiseimmunity is desired. It may be desirable to elfect greater gain of thelatter signals without unduly increasing the complexity of the matrixingapparatus. The apparatus of FIG. 3 eflects such result. In describingthe apparatus of FIG. 3 and of other figures hereinafter, terminalscorresponding to the terminals in the apparatus 16 of FIG. 1 areidentified by the same reference numerals to indicate that they would beconnected to the other portions of the television receiver as thecorresponding terminals in apparatus 16 are connected thereto.

The matrixing apparatus 316 of FIG. 3 comprises a pair of signal sourcesfor individually supplying diiferent ones of the aforementioned I and Qsignals, these sources including individual pairs of output terminalshaving a common terminal. More specifically, one of such sourcescomprises a chromaticity-signal detector having a pair of outputcircuits and a low-pass filter network 61 preferably having a pass bandof 01.5 megacycles, a phase inverter 62, and a triode 63 coupled incascade, in the order named, to one of the output circuits of the unit60. The triode 63 includes a pair of output terminals 70, 69 coupled,respectively, in the anode and cathode circuits thereof. The other ofsuch sources includes the unit and a low-pass filter network 64preferably having a pass band of 0-500 kilocycles and a triode 65coupled in cascade, in the order named, to the other output circuit ofthe unit 60. The triode 65 includes a pair of output terminals 68, 69coupled, respectively, in the anode and cathode circuits thereof. Aplurality of input circuits of the detector 60 individually includedifferent ones of the pair of terminals 30, 30, 26, 26, and 24 24. Theunit 60 may 'be of conventional type for deriving positive I and Qsignals from an applied modulated subcarrier wave signal. For example,

it may comprise the balanced detector circuit of FIG. 1 including thediodes 40, 41 and 43, 44 with the polarity of the diodes 40, 41 the sameas that of the diodes 43, 44 and without the impedance network 52. Insuch detector the positive I and Q signals are developed across thesecondary windings of the transformers 45 and 42, respectively, and suchwindings would be coupled to the input circuits of the units 61 and 64,respectively, in FIG. 3.

The apparatus 316 of FIG. 3 also includes an impedance network,specifically, the anode and cathode load circuits of the tubes 65 and 63coupled, respectively, to the pair of output terminals 68, 69 and 70,69. Such network includes three load circuits each having two terminals,one of which is common to the three load circuits with the otherterminal of one thereof coupled to the common output terminal 69 andwith the other terminals of the others of the load circuits individuallycoupled to different ones of the other output terminals 68 and 70 forcausing currents representative of both of the supplied signals to flowthrough each of these load circuits. More specifically, these three loadcircuits comprise a cathode resistor 74 coupled in a common cathodecircuit for the tubes 63 and 65, one terminal of the resistor 74 beingconnected to the common output terminal 69 and the other thereofconnected to chassisground. Chassis-ground is the common terminal forthe three load circuits of the impedance network being described. Asecond of these load circuits comprises a cathode resistor 75 coupledbetween the aforementioned output terminal 69 and the cathode of thetube 65 and further comprises an anode load impedance. This anodeimpedance comprises in series a resistor 76 having one terminal thereofcoupled to the anode of the tube 65 and to the aforementioned outputterminal 68, and a source of B potential 77 having the negative terminalthereof connected to the common terminal for the three load circuits,that is, to chassis-ground. The third load circuit comprises an anodeload impedance including a load resistor 79 connected to the anode ofthe tube 63 and the aforementioned output terminal 70 connected inseries with the source 77. The second and third loali circuits may beconsidered to include a tapped resistor 78 connected between the anodesof the tubes 63 and 65 and a phase-inverter amplifier including a triode71 having the control electrode thereof connected to the tap of theresistor 78. The triode 71 includes an anode load resistor 73 and acathode resistor 72. It is apparent that currents representative of bothof the applied signals +Q and I flow through each of the above-describedload circuits. As will be explained more fully hereinafter, theimpedances of these three load circuits are so proportioned relative toeach other that the currents flowing through different ones thereofindividually represent the other different components of the color,specifically, the color-difference components GY, R-Y, and BY.

Operation of matrixing apparatus of FIG. 3

Briefly considering now the operation of the matrixing apparatus 316,the modulated subcarrier wave signal is applied through the terminals30, 30 to an input circuit of the chromaticity-signal detector 60 whileproperly phased signals developed in a generator, such as the unit 23 ofFIG. 1, are applied through the pairs of terminals 26, 26 and 24, 24 tothe detector 60 so as individually to heterodyne with the modulatedsubcarrier wave signal in a manner previously explained more fullyherein and also in the aforementioned Electronics article to develop Iand Q outputs signals. Those components of the 1 signal developed in theunit 60 and having frequencies below 1.5 megacycles are translatedthrough the filter network 61, inverted in phase by the inverter 62, andapplied to the control electrode of the tube 63 to develop a +1 signalin the anode circuit and a -I signal in the cathode circuit of the tube63. Those components of the Q signal developed in the output circuitof'the detector 60 having frequencies below 500 kilocycles aretranslated through the network 64 and applied to the control-electrodecircuit of the tube 65 to develop Q signals in the anode and +Q signalsin the cathode circuits of the tube 65. Considered broadly, the tubes 65and 63 are generators such as the units K Q and K 1 of FIG. 2 Thecathode load resistor 74 corresponds to the resistor R of FIG. 2b andthe resistors 76 and 79 correspond, respectively, to the resistors R andR,- of FIG. 2 The bridging resistor 78 is solely a means for derivingwith desired phase and magnitude the color-diiference signal (BY)effectively developed substantially as a positive BY signal across thecathode resistor 74. The currents flowing through the resistors 76, 79,and 74 represent, respectively, the color-difference signals G-Y, R-Y,and BY. Though the current flowing through the resistor 74 representsthe positive signal BY, it is preferred in the embodiment of FIG. 3 toderive the negative signal (B-Y) from the bridging resistor 78 throughwhich portions of the currents developed by the I and Q signals appliedto the tubes 63 and 65 fiow in opposing directions as they also flow inthe resistor 74.

Referring again to FIG. 2a, it should be noted, as previously mentionedherein, that negative portions of Q and I are required to develop thecolor-difference signal G-Y, positive portions of the Q and I signalsare required to develop the signal R-Y, and a positive portion of Qsignal and a negative portion of the I signal are required to developthe signal BY. The resistors 74-76, inclusive, 78, and 79 areproportioned to effect suchresults while the amplifier stage includingthe tube 71 is proportioned to increase the magnitude of the (BY) signaldeveloped at the tap on the resistor 78 and to invert such signal sothat the positive BY signal developed across the terminals 32, 32 isproperly related in magnitude and sense to the positive G--Y and RYsignals developed across the terminals 31, 31 and 33, 33, respectively.In view of the consideration given with respect to the mathematicalanalysis of such a circuit to determine such proportioning in FIG. 1, itis not believed necessary to include a detailed mathematical analysisfor the circuit of FIG. 3. However, a general explanation of the mannerof proportioning will now be presented.

Referring to the vector diagram of FIG. 2a, it is noted that, in orderto develop the signal GY in terms of Equation 3 above, a fraction .65 ofa negative Q signal is required and a fraction .27 of a negative Isignal is required. Referring to the tube 65 in FIG. 3, it is noted thata negative Q signal is developed in the anode circuit thereof while apositive Q signal is developed in the cathode circuit thereof. In theanode and cathode circuits of the tube 63, positive and negative Isignals, respectively, are developed. The signal I in the cathodecircuit of the tube 63 causes a I signal to be developed in the anodecircuit of the tube 65 in a conventional manner and the load resistors76 and 75 together with the common resistor 74 together with any otherparameters of the circuits which affect the signals developed in theanode circuits of the tubes 63 and 65 are proportioned so that thequantities of -I and Q signals at the terminal 68 are in the ratio of.65Q and .271. In such proportioning the effects of currents flowingthrough the resistor 78 should also be considered as such effects mayrequire compensation by a change in the proportioning of the magnitudesof other circuit parameters. In order to develop the RY signal inaccordance with Equation 1 above, the portions +.96I and +.62Q arerequired. The positive I signal developed at the terminal 70 combineswith a positive Q signal developed at the terminal 70 by application ofa +Q signal from the cathode of the tube 65 to the cathode of the tube63. The signals combine in the proper proportions due to theproportioning of the resistors 74, 79, and

78 as well as the resistor 75 in the cathode circuit of the tube 65.Agaip, as previously mentioned, the effect of the current flowing in theresistor 78 should be considered in determining the proportioning ofthese resistors to develop the proper proportions of I and Q signals atthe terminal 70, and other parameters of the tube may also requireconsideration of the type normally made when designing tube circuits. Inorder to develop the positive B-Y signal in accordance with Equation 2above, the portions 1.l1I and +1.70Q of the I and Q signals arerequired. +Q and I signals are developed across the cathode loadresistor 74 and such may be used to provide the B-Y signal as willbecome more understandable by considering FIG. 4 hereinafter. However,pure -Q and +1 signals may also be considered to be present across theresistor 78, if the contamination of the Q signal by a fraction of the Isignal at the upper terminal of the resistor 78 is compensated for by anexcess of the I signal applied to the lower terminal and similarly ifthe contaminated I signal at the lower terminal is corrected by anexcess of Q signal at the upper terminal. In other words, though pure Qand +I signals may not be present at the end terminals of the resistor78, effectively such signals are present when considering the currentflowing through the resistor 78. Such current is substantially thatwhich pure Q and +1 signals would develop. The negative Q signal at theterminal 68 combines in the resistor 78 with the positive I signal atthe terminal 70 to develop at a properly selected tap point of theresistor 78 a negative BY signal having the Q and I signals in theproportions just mentioned. The triode 71 acts as a phase inverter todevelop the positive B-Y signal from the negative B-Y signal and as anamplifier to provide an adequate magnitude for the positive B-Y signal.

The mathematical analysis required to develop the proper proportions ofthe I and Q .si'gnals'in the proper senses at the different pointsmentioned above may be developed by a straightforward technique ofcircuit analysis. Some indication of the degree and manner of suchproportioning may be obtained by considering the vector diagram of FIG.2a. In considering such vector diagram, it is noted that if the I and Qvectors are spread apart in angular relation so as individually tocoincide with the RY and G-Y vectors, the colordifference signalsrepresented by the latter vectors will thereby be obtained. The cathoderesistor 74 is effective to cause such spreading of the vectors.However, since the vector R-Y is displaced by approximately 33 withrespect to the vector I While the vector G-Y is only displaced byapproximately 23 with respect to the vector Q, the spreading of the Qvector should not be as great as the spreading of the I vector and,therefore, the additional cathode resistor 75 is connected in thecathode circuit of the tube 65 to minimize the effect on the I signal.The resistors 76 and 79 then may be considered to be proportioned'todevelop proper magnitudes of the RY and G-Y signals. Considering thevector diagram of FIG. 2a with reference to obtaining the BY signal fromthe I and Q signals, it should be noted that if a line is placed betweenthe ends of the vectors RY and (G-Y) obtained from the signals +1 and Q,a negative B-Y vector will intersect such line at some intermediatepoint thereof. The tapped position on the resistor 78 represents suchintersection point, and the tube 71 with the circuit parameters thereofinverts the negative B-Y signal to a positive BY signal and providesadequate gain so that the signals G--Y, B-Y, and RY developed across thepairs of terminals 31, 31, 32, 32, and 33, 33, respectively, are in theproper relative magnitudes.

While applicant does not intend to be limited to any particular circuitdesign, design information has been developed which has been founduseful in practicing the invention. In determining the magnitudes of thecircuit parameters for such design, preliminary considerations ofadequate band width and gain for the amplifiers were resolved byselecting appropriate values for the resistors 79 and 73 to ensure suchgain and band width. There follows a tabulation of such designinformation:

Upper portion, 3,500 ohms; lower portion 8,500 ohms. Description ofembodiment of FIG. 4

FIG. 4 is a circuit diagram of a modified form of a portion of thematrixing apparatus of FIG. 3, specifically, that portion of thematrixing apparatus comprising substantially only the impedance network.In view of the relationship of the circuits of FIG. 3 and FIG. 4,similar ele ments in these circuits are identified by the same referencenumerals while analogous circuit elements are represented in the circuitof FIG. 4 by a reference numeral similar to that of the analogouselement in FIG. 3 but with 400 added thereto.

The impedance network of FIG. 4 is essentially the same as the corresonding network of FIG. 3, differing principally in having a pair ofcathode resistors 478a and 4781) instead of the resistors 75 and 78 inthe circuit of FIG. 3. Because of this change, there are also some minorchanges in the circuit connections to the triode 471 in the embodimentof FIG. 4. As in the corresponding portion of FIG. 3 the triodes 63 and65 have output terminals 68, 69 and 70, 69, respectively. The anode loadresistors 76 and 79 comprise two of the three load circuits in theimpedance network. The third load circuit is the resistor 74 coupled tothe cathodes of the tubes 65 and 63 through the cathode load resistors478a and 47811, respectively. The terminal 69 and, therefore, the loadresistor 74 are directly connected to the cathode of the amplifier tube471, the control electrode of which is connected to chassis-ground forother than unidirectional potentials. It should be understood that theadmittance looking into the tube 471 is so large with respect to themagnitude of the resistor 74 that the circuit including the tube 471 isa major factor in determining the potential developed across theresistor 74. The anode circuit of the tube 471 includes the anode loadresistor 73 and is connected to the pair of output terminals 32, 32.

Operati n of embodiment of FIG. 4

In general, the network of FIG. 4 operates in the same manner as thecorresponding network of FIG. 3. A positive signal Q is applied throughthe terminals 67, 67 to the control electrode of the tube 65 anddevelops a negative Q signal in the anode circuit thereof and a positiveQ signal in the cathode circuit thereof. Similarly, a negative signal Iis applied through the terminals 66, 66 to the control electrode of thetriode 63 to develop a positive I signal in the anode thereof and anegative I signal in the cathode thereof. As explained with reference tothe corresponding circuit of FIG. 3, the negative Q signal in the anodecircuit of the tube 65 combines with the proper amount of a negative Isignal developed across the oathode load resistor 74 and, therefore,developed in the anode circuit of the tube 65 to develop a G-Y signalacross I the load resistor 76 for application through the terminals 31,31 to one of the control ducing device. Similiarly, of I and Q signalsare electrodes in an image-reproproper magnitudes and polaritiesdeveloped across the anode load resistor 79 of the tube 63 to develop anRY signal for application through the terminals 33, 33 to anothercontrol electrode of an image-reproducing device. The cath ode loadresistors 478a and 4781; act in a manner similar to that of the resistor78 of FIG. 3 to combine proper portions of -I and +Q signals to developa positive BY signal at the terminal 69 and across the resistor 74. Thispositive BY signal is applied to the cathode of the amplifier 471wherein it is amplified by an appropriate amount to develop a BY signalacross the anode load resistor 73 for application through the terminals32, 32 to the third control electrode of the image-reproducing device.

The circuit analysis of the impedance network of FIG. 4 can be made in amanner similar to that described with reference to the correspondingnetworks of FIGS. 3 and l.

Description of embodiment of FIG. 5

The matrixing apparatus of FIG. 5 closely corresponds to the matrixingapparatus 16 of FIG. 1 and, therefore, similar elements in theseembodiments are identified by the same reference numerals whileanalogous circuit elements are represented in the embodiment of FIG. 5by a reference numeral similar to that of the analogous element in FIG.1 but with 500 added thereto.

The matrixing apparatus 16 of FIG. 1, as has previously been statedherein, is a simple apparatus for developing the desiredcolor-difference signals. However, to make the most efficientutilization of the information on a sub carrier wave signal having asmodulation components a wide band I and a narrow band Q signal, it isdesirable to have channels through which the I and Q signals aretranslated which have pass bands which correspond to the band widths ofthe transmitted I and Q signals. The matrixing apparatus of FIG. 5includes such channels essentially by rearranging the input circuits tothe matrixing apparatus so that the I and Q signals are applied throughthe transformers 45 and 42, respectively, while the locally generatedsignal is applied through the transformer 546. The supply circuitincludes a band-pass filter network 80 preferably having a pass band of3.2-4.0 megacycles coupled between a pair of input terminals 21, 21 andthe primary winding of the transformer 42 and a 90 phase shifter 525 anda bandpass filter network 81 preferably having a pass band of 2.5-4.3megacycles coupled in cascade between the input terminals 21, 21 and theprimary winding of the transformer 45. The transformers 42 and 45 havedifferent primary-to-secondary turns ratios in the ratio of 43513.? 3,respectively, for the purpose of applying Q and I signals withmagnitudes in this ratio to the balanced detectors. The primary windingof the transformer 546 is connected to the pair of terminals 24, 24. Thebalanced detectors including the diodes 40, 41 and 43, 44 as well as theload circuits 53g, 53b, and 53r are the same as the correspondingdetectors and load circuits in the apparatus 16 of FIG. 1. Adirect-current restorer circuit such as the unit 56 of FIG. 1 may becoupled through the terminals 54, 54 to the load circuits 53g, 53b, and531.

Operation of embodiment of FIG. 5

Though the input circuits to the apparatus of FIG. 5 are different fromthe corresponding input circuits of the apparatus 16 of FIG. 1, thebalanced detectors for deriving the modulation components +1 and -Q andthe load circuits for developing the color-difference signals GY, RY,and BY operate in a manner similar to the corresponding units of FIG. 1.In the apparatus of FIG. 5, a composite video-frequency signal such asamplified in a unit such as the unit plied through the terminals 21, 21to input circuits of the units 80 and 525 in the apparatus of FIG. 5.That portion of the signal applied to the filter network 80 havingfrequencies between 3.2 and 4 megacycles is translated through the unit80 and coupled by means of the transformer 42 to the balanced detectorincluding the diodes 40 and 41 with one magnitude. At least the upperfrequencies of the signal applied to the unit 525 are shifted in phaseby 90 and those frequencies between 13 of FIG. 1 is ap-.

2.5 and 4.3 megacycles are translated through the network 81 and coupledthrough the transformer 45 to that balanced detector including thediodes 43 and 44 with another magnitude, these magnitudes being in theratio of 4.35:3.73 for the Q and I signals, respectively. A locallygenerated signal in proper phase and frequency with respect to thesignals applied through the transformers 42 and 45, more specifically, asignal such as developed in a generator such as the unit 23 of FIG. 1,is applied through the terminals 24, 24 and the transformer 546 to bothof the previously mentioned balanced detectors. In a manner similar tothat described with reference to the apparatus 16 of FIG. 1, the +1 and-Q modulation components are derived from the modulated subcarrier wavesignal and developed, respectively, across the terminals 49, 51 and 49,50. These I and Q signals differ from the corresponding signals in FIG.1 in that the Q signal has a band width of approximately 500 kilocyclesand the 1 signal has a band width of approximately 1.5 megacycles. Theload circuits 53g, 53b, and 531' utilize such I and Q signals in themanner described with reference to the apparatus 16 of FIG. 1 to developG-Y, BY, and R-Y color-difference signals across the pairs of terminals31, 31, 32, 32, and 33, 33, respectively, for application to controlelectrodes of an image-reproducing device such as the unit 14 of FIG. 1.

While there have been described what areat present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed to cover all such changes and modifications as fall within thetrue spirit and scope of the invention.

What is claimed is:

1. Matrixing apparatus for a color-television system for developing froma pair of signals individually representative of different components ofthe color of a televised image signals representative of other differentcomponents of said color of said image comprising: a pair of signalsources for individually supplying different ones of said pair ofsignals, said sources having a common output terminal and two otheroutput termlnals; and an impedance network coupled to said sources andincluding three load circuits each having two terminals one of which iscommon to said three load circuits with the other terminal of onethereof coupled to said common output terminal of said sources and withthe other terminals of the others of said load circuits individuallycoupled to different ones of said other output terminals of said sourcesfor causing currents representative of both of said supplied signals toflow through each of said load circuits, the impedances of said loadcircuits being so proportioned relative to each other that the currentsflowing through different ones thereof individually represent said otherdifferent components of said color.

2. In a color-television receiver, matrixing apparatus for developingthree color-representative signals from two modulation components at twodifferent phase angles of a received color subcarrier signal comprising:two sources each for supplying one of said two modulation components;three load circuits; and means for connecting the sources and three loadcircuits in a network of three parallel branches comprising one loadcircuit-in parallel with another load circuit and one source in series,and in parallel with the remaining load circuit and source in series,said sources and load circuits being so proportioned that the twomodulation components mix in each of the load circuits in proportionsand senses to develop one of three color-representative signals in eachof the load circuits.

3. In a color-television receiver, matrixing apparatus for developingred, green, and blue color-difference signals from two modulationcomponents at two different phase angles of a received color subcarriersignal comprising: two sources each for supplying one of said twomodulation components; three loadcircuits; and means for connecting thesources and three load circuits in a network of three parallel branchescomprising one load circuit in parallel with another load circuit and onsource in series, and in parallel with the remaining load circuit andsource in series, said sources and load circuits being so proportionedthat the two modulation components mix in each of the load circuits inproportions and senses to develop one of the red, green, and blue colordifference signals in each of the load circuits.

4. In a color-television receiver, matrixing apparatus for developingthree color-representative signals from two modulation components at twodifferent phase angles of a received color subcarrier signal comprising:two sources each for supplying oneof said two modulation compoents;three load circuits; means for connecting the sources and three loadcircuits in a network of three parallel branches comprising one loadcircuit in parallel with another load circuit and one source in series,and in parallel with the remaining load circuit and source in series,said sources and load circuits being so proportioned that the twomodulation components mix in each of the load circuits in proportionsand senses to develop one of the three color-representative signals ineach of the load circuits; and means for deriving one of said threecolorrepresentative signals from each of the load circuits.

5. In a color-television receiver, matrixing apparatus for developingred, green, and blue color-difference signals from two modulationcomponents at two different phase angles of a received color subcarriersignal comprising: two sources each for supplying one of said twomodulation components; three load circuits; means for connecting thesources and three load circuits in a network of three parallel branchescomprising one load circuit in parallel with another load circuit andone source in series, and in parallel with the remaining load circuitand source in series, said sources and load circuits being soproportioned that the two modulation components mix in each of the loadcircuit in proportions and senses to develop one of the red, green, andblue color-difierence signals in each of the load circuits; and meansfor deriving one of said three color-difierence signals from each of theload circuits.

6. In a color-television receiver, said color-television receiveradapted to receive a color-television signal, said color-televisionsignal including a color subcarrier containing a plurality of colorsignals, each of said color signals corresponding to a predeterminedsignal phase, matrix means adapted to accept a first plurality ofsignals corresponding to a first group of predetermined signal phases insaid color subcarrier to yield a second plurality of signalscorresponding to a second group of predetermined signal phases, s'aidmatrix means comprising in combination, a plurality of transmissionnetworks, each of said transmission networks having a first controlelectrode, a second control electrode, and an output electrode, a mutualimpedance coupled to the first control electrode of each of saidtransmission networks to cause any signal developed in one transmissionnetwork to drive each of the other transmission networks, means forcoupling each of said plurality of signals to the second controlelectrode of a prescribed group of said transmission net-workscorresponding in number to said first plurality of signals, means forutilizing said mutual impedance to produce signal addition ofdeterminable amplitudes and polarities of said first plurality ofsignals at the output terminals of each of said transmission networks tocause each signal of said second plurality of signals to appear at theoutput terminal of one of said plurality of transmission networks.

7. In a color-television receiver adapted to receive at least achrominance signal, the combination of means to demodulate a first andsecond color-difference signal from said chrominance signalcorresponding to prescribed angles of said chrominance signal, aplurality of amplir modulator means to demodulate a fiers having amutual cathode resistor, means for applying said first and secondcolor-dilference signals to selected amplifiers of said plurality, meansfor adding selected amplitudes and polarities of said first and secondcolor-difference signals in said plurality of amplifiers to develop atleast a trio of color-difference signals corresponding to angles of saidchrominance signal other than said prescribed angles.

8. In a color-television receiver adapted to receive at least achrominance signal, the combination of demodulator means to demodulate afirst and second color-difference signal from said chrominance signalcorresponding to information at' determinable angles of said chrominancesignal, a trio of electron steam devices each having output circuits andcoupled to cause modulation introduced in one electron stream to providecorresponding modulations in the other electron stream devices, meansfor modulating the electron streams of a pair of said trio with saidfirst and second color-difference signals respectively, means forcausing signal addition in each of said trio due to said coupling todevelop each of a trio of color-difference signals corresponding toangles of said chrominance signal other than the angles corresponding tosaid first and second color-difference signals in each output circuit.

9. In a color-television receiver adapted to receive a color-televisionsignal including a chrominance signal wherein different color-differencesignals occur at different phases; the combination of: a firstdemodulator means to demodulate a first color-dilferelrce signal from afirst phase of said chrominance signal, a second desecondcolor-difference signal from a second phase of said chrominance signal,a first and second electron tube each having a cathode and an anode anda control electrode, a fixed potential point, a cathode resistor coupledfrom the cathodes of said first and second electron tubes to said fixedpotential means, circuit means coupled between the anodes of said firstand second electron tubes and said fixed potential point to render saidfirst and second electron tubes operative whereby signals applied to thecontrol electrodes of said first and second electron tubes will 'becombined across said cathode resistor, means coupling said first andsecond demodulator means to the control electrodes of said first andsecond electron tubes respectively to apply said first and secondcolor-difference signals to the control electrodes of said first andsecond electron tubes respectively whereby a third color-differencesignal representing signal combinations of prescribed polarities of saidfirst and second color-difiference signals is developed across saidcathode resistor.

10. In a color-television receiver adapted to receive a color-televisionsignal including a chrominance signal wherein different color-differencesignals occur at dilterent phases, the combinaton of: a firstdemodulator means to demodulate a first color-difference signal from afirst phase of said chrominance singal, a second demodulator means todemodulate a second color-difference signal from a second phase of saidchrominance signal, a first and second amplifier each having an inputterminal and cathode and both having a common out-put load operativelyconnected therewith to each cathode to produce a signal combination ofsignals applied to the input terminals of said first and secondamplifiers, and means coupling said first and second demodulator meansto the input terminals of said first and second amplifiers respectivelyto develop a color-difference signal representing a signal combinationof said first and second color-difference signals across said commonoutput load.

11. In a color-television receiver adapted to receive a color-televisionsignal including a chrominance signal wherein difierent color-differencesignals occur at different phases, the combination of: first demodulatormeans to demodulate a first color-difierence signal from a first phaseof said chrominance signal, second demodulator means to demodulate asecond color-difference signal from a second and different phase of saidchrominance signal, an amplifier having an input circuit and a first andsecond output load and operatively connected to develop differentpolarities of a signal across said first and second output loads inresponse to that signal applied to said input circuit, means couplingsaid first demodulator means to said input circuit to apply said firstcolor-difference signal to said input circuit to develop differentpolarities of said first color-difference signal across said first andsecond output loads, and means coupling said second demodulator means toone of said first and second output loads to produce a signalcombination of said first and second colordifference signals across atleast one of said first and second output loads.

' 12. In a color-television receiver, matrixing apparatus for developingfrom two modulation components, occurring at two prescribed angles of areceived color subcarrier signal, at least two color-representativesignals at angles other than said prescribed phase angles, comprising:two source means, each for supplying one of said two modulationcomponents; and load circuit means coupled to the sources for matrixingthe two modulation components in three portions of the load circuit, oneportion of which is coupled in common to the other two, in proportionsand senses to develop said color-representative signals at said otherphase angles in the load circuit.

13. In a color-television receiver adapted to receive at least achrominance signal, matrixing apparatus comprising: means for providingfirst and second color-representative signals from said chrominancesignal at prescribed phase angles thereof; a pair of circuit loops;means for applying said first and second color-representative signalsindividually to corresponding ones of said circuit loops; and meansincluding an impedance circuit coupled in common to said pair of circuitloops for cross-coupling selected amplitudes and polarities of saidfirst and second colorrepresentative signals between said pair ofcircuit loops to develop at least two new color-representative signalsat angles of said chrominance signal other than said prescribed angles.

14. Matrixing apparatus for a color-television system for developingfrom a pair of signals individually representative of differentcomponents of the color of a televised image, signals representative ofother different components of said color of said image comprising: apair of signal sources for individually supplying different ones of saidpair of signals; and an impedance network having two circuit loopsindividually coupled to said sources and including three impedanceelements, one of which is common to said two circuit loops, for causingcurrents representative of both of said supplied signals to flow througheach of said impedance elements, the impedances of said elements beingso proportioned relative to each other that the currents flowing throughdifferent ones thereof individually represent said other differentcomponents of said color.

15. In a color television receiver including a source of a chrominancesignal comprising phase and amplitude modulated color subcarrier waves,the modulation of said color subcarrier waves being such thatdemodulation of said waves at a first predetermined phase will produce aR-Y signal, demodulation of said waves at a second predetermined phasewill produce a B Y signal, and demodulation of said waves at a thirdpredetermined phase will produce a GY signal, said receiver alsoincluding a source of reference oscillations of color subcarrierfrequency, and color image reproducing apparatus adapted to reproducecolor images in response to the delivery of R-Y, BY, and GY signals,respectively, to respective first, second and third input terminalsthereof, a color demodulator system comprising in combination: first andsecond demodulating means each having separate output circuit means fordeveloping respectively different first and second color signal outputs,means for applying reference oscillations from said source to said firstdemodulating means in a fourth predetermined phase different from any ofsaid first, second and third predetermined phases, means for applyingreference oscillations from said source to said second demodulatingmeans in a fifth predetermined phase different from any of said first,second, third and fourth predetermined phases, means for applyingmodulated, color subcarrier waves from said chrominance signal source toeach of said first and second demodulating means, and common outputcircuit means coupled to both of said first and second demodulatingmeans for providing a third color signal output and for causinginteraction between said first and second demodulating means such thatthe first color signal output produced in the separate output circuitmeans of said first demodulating means corresponds to one of said .R-Y,GY and BY signals, the second color signal output produced in theseparate output circuit means of said second color demodulator meanscorresponds to a second one of said R-Y, GY and BY signals, and thethird color signal output produced in the common output circuit means ofboth of said first and second demodulating means corresponds to theremaining one of RY, GY and BY signals, and means for coupling saidfirst, second and third input terminals to the respectively appropriateoutput circuit means.

16. In a color television receiver including a source of a chrominancesignal comprising phase and amplitude modulated color subcarrier wavesrepresentative of RY signal information at a first predetermined phase,representative of BY signal information at a second predetermined phase,and representative of GY signal information at a third predeterminedphase, said receiver also including a source of reference oscillationsof said color subcarrier frequency, and color signal utilization meansrequiring the delivery of R-Y, BY and GY signals, respectively, to therespective first, second and third input terminals thereof, thecombination comprising: first and second demodulating means forheterodyning said modulated subcarrier wave with reference oscillationsto produce respectively different color difference signal outputs inrespectively separate output circuit means, means for applying modulatedcolor subcarrier waves from said chrominance signal source to each ofsaid first and second demodulating means, means for separately applyingto each of said first and second demodulating means referenceoscillations of respectively different selected phases different fromany of said first, second and third predetermined phases, whereby theheterodyning action in each of said demodulating means is such as toproduce respective color signal outputs in the respective separateoutput circuit means which are representative of signal informationother than said R-Y, BY and GY signals in the absence of interactionbetween said first and second demodulating means, and means for causinginteraction between said first and second demodulating means such thatthe color signal outputs produced in the respectively separate outputcircuit means of said first and second demodulating means arerepresentative of different ones of said R-Y, BY and GY signals, saidinteraction causing means comprising impedance means common to both ofsaid first and second demodulating means for combining signals from bothsaid first and second demodulating means and for influencing said signalproduction in both of said respectively separate output circuits, meansfor deriving the remaining one of said RY, BY and GY signals from saidcommon impedance means, and means for supplying the required signalinformation to each of said first, second and third input terminals fromthe respectively appropriate one of said separate output circuit meansand output signal deriving means.

(References 011 following page) References Cited UNITED STATES PATENTSGreen 333-70 Weagant 250-27.16 Clark 25027.16 Hoeppner 333-70 Eltgroth333-70 Lovell 250-27.16 Schlesinger 17s- 5.4 Parker 178-5.4

22 OTHER REFERENCES 7 Principles of NTSC Compatible Color Television,Electronics, February 1952, pp. 8895.

RCA Review, June 1953, pp. 205-226.

5 JOHN W. CALDWELL, Acting Primary Examiner.

DAVID REDINBAUGH, ROBERT H. ROSE,

STEPHEN W. CAPELLI, Examz ners.

NEWTON N. LOVEWELL, J. A. OBRIEN,

L. P. SPECK, R. SEGAL, R. MURRAY,

Assistant Examiners.

6. IN A COLOR-TELEVISION RECEIVER, SAID COLOR-TELEVISION RECEIVERADAPTED TO RECEIVE A COLOR-TELEVISION SIGNAL, SAID COLOR-TELEVISIONSIGNAL INCLUDING A COLOR SUBCARRIER CONTAINING A PLURALITY OF COLORSIGNALS, EACH OF SAID COLOR SIGNALS CORRESPONDING TO A PREDETERMINEDSIGNAL PHASE, MATRIX MEANS ADAPTED TO ACCEPT A FIRST PLURALITY OFSIGNALS CORRESPONDING TO A FIRST GROUP OF PREDETERMINED SIGNAL PHASE,PHASES IN SAID COLOR SUBCARRIER TO YIELD A SECOND PLURALITY OF SIGNALSCORRESPONDING TO A SECOND GROUP OF PREDETERMINED SIGNAL PHASES, SAIDMATRIX MEANS COMPRISING IN COMBINATION, A PLURALITY OF TRANSMISSIONNETWORKS, EACH OF SAID TRANSMISSION NETWORKS HAVING A FIRST CONTROLELECTRODE, A SECOND CONTROL ELECTRODE, AND AN OUTPUT ELECTRODE, A MUTUALIMPENDENCE COUPLED TO THE FIRST CONTROL ELECTRODE OF EACH OF SAIDTRANSMISSION NETWORKS TO CAUSE ANY SIGNAL DEVELOPED IN ONE TRANSMISSINNETWORK TO DRIVE EACH OF THE OTHER TRANSMISSION NETWORKS, MEANS FORCOUPLING EACH OF SAID PLURALITY OF SIGNALS TO THE SECOND CONTROLELECTRODE OF A PRESCRIBED GROUP OF SAID TRANSMISSION NETWORKSCORRESPONDING IN NUMBER TO SAID FIRST PLURALITY OF SIGNALS, MEANS FORUTILIZING SAID MUTUAL IMPEDANCE TO PRODUCE SIGNAL ADDITION OFDETERMINABLE AMPLITUDES AND POLARITIES OF SAID FIRST PLURALITY OFSIGNALS AT THE OUTPUT TERMINALS OF EACH OF SAID TRANSMISSION NETWORKS TOCAUSE EACH SIGNAL OF SAID SECOND PLUALITY OF SIGNALS TO APPEAR AT THEOUTPUT TERMINAL OF ONE OF SAID PLURALITY OF TRANSMISSION NETWORKS. 12.IN A COLOR-TELEVISION RECEIVER, MATRIXING APPARATUS FOR DEVELOPING FROMTWO MODULATION COMPONENTS, OCCURRING AT TWO PRESCRIBED ANGLES OFRECEIVED COLOR SUBCARRIER SIGNAL, AT LEAST TWO COLOR-REPRESENTATIVESIGNALS AT ANGLES OTHER THAN SAID PRESCRIBED PHASE ANGLES, COMPRISING:TWO SOURCE MEANS, EACH FOR SUPPLYING ONE OF SAID TWO MODULATIONCOMPONENTS; AND LOAD CIRCUIT MEANS COUPLED TO THE SOURCES FOR MATRIXINGTHE TWO MODULATION COMPONENTS IN THREE PORTIONS OF THE LOAD CIRCUIT, ONEPORTION OF WHICH IS COUPLED IN COMMON TO THE OTHER TWO, IN PROPORTIONSAND SENSES TO DEVELOP SAID COLOR-REPRESENTATIVE SIGNALS AT SAID OTHERPHASE ANGLES IN THE LOAD CIRCUIT.
 15. IN A COLOR TELEVISION RECEIVERINCLUDING A SOURCE OF A CHROMINANCE SIGNAL COMPRISING PHASE ANDAMPLITUDE MODULATED COLOR SUBCARRIER WAVES, THE MODULATION OF SAID COLORSUBCARRIER WAVES BEING SUCH THAT DEMODULATION OF SAID WAVES AT A FIRSTPREDETERMINED PHASE WILL PRODUCE A R-Y SIGNAL, DEMODULATION OF SAIDWAVES AT A SECOND PREDETERMINED PHASE WILL PRODUCE A B-Y SIGNAL, ANDDEMODULATION OF SAID WAVES AT A THIRD PREDETERMINED PHASE WILL PRODUCE AG-Y SIGNAL, SAID RECEIVER ALSO INCLUDING A SOURCE OF REFERENCEOSCILLATIONS OF COLOR SUBCARRIER FREQUENCY, AND COLOR IMAGE REPRODUCINGAPPARATUS ADAPTED TO REPRODUCE COLOR IMAGES IN RESPONSE TO THE DELIVERYOF R-Y, B-Y, AND G-Y SIGNALS, RESPECTIVELY, TO RESPECTIVE FIRST, SECONDAND THIRD INPUT TERMINALS THEREOF, A COLOR DEMODULATOR SYSTEM COMPRISINGIN COMBINATION: FIRST AND SECOND DEMODULATING MEANS EACH HAVING SEPERATEOUTPUT CIRCUIT MEANS FOR DEVELOPING RESPECTIVELY DIFFERENT FIRST ANDSECOND COLOR SIGNAL OUTPUTS, MEANS FOR APPLYING REFERENCE OSCILLATIONSFROM SAID SOURCE TO SAID FIRST DEMODULATING MEANS IN A FOURTHPREDETERMINED PHASE DIFFERENT FROM ANY OF SAID FIRST, SECOND AND THIRDPREDETERMINED PHASES, MEANS FOR APPLYING REFERENCE OSCILLATIONS FROMSAID SOURCE TO SAID SECOND DEMODULATING MEANS IN A FIFTH PREDETERMINEDPHASE DIFFERENT FROM ANY OF SAID FIRST, SECOND, THIRD AND FOURTHPREDETERMINED PHASES, MEANS FOR APPLYING MODULATED, COLOR SUBCARRIERWAVES FROM SAID CHROMINANCE SIGNAL SOURCE TO EACH OF SAID FIRST ANDSECOND DEMODULATING MEANS, AND COMMON OUTPUT CIRCUIT MEANS COUPLED TOBOTH OF SAID FIRST AND SECOND DEMODULATING MEANS FOR PROVIDING A THIRDCOLOR SIGNAL OUTPUT AND FOR CAUSING INTERACTION BETWEEN SAID FIRST ANDSECOND DEMODULATING MEANS SUCH THAT THE FIRST COLOR SIGNAL OUTPUTPRODUCED IN THE SEPARATE OUTPUT CIRCUIT MEANS OF SAID FIRST DEMODULATINGMEANS CORRESPONDS TO ONE OF SAID R-Y, G-Y AND B-Y SIGNALS, THE SECONDCOLOR SIGNAL OUTPUT PRODUCED IN THE SEPARATE OUTPUT CIRCUIT MEANS OFSAID SECOND COLOR DEMODULATOR MEANS CORRESPONDS TO A SECOND ONE OF SAIDR-Y, G-Y AND B-Y SIGNALS, AD THE THIRD COLOR SIGNAL OUTPUT PRODUCED INTHE COMMON OUTPUT CIRCUIT MEANS OF BOTH OF SAID FIRST AND SECONDDEMODULATING MEANS CORRESPONDS TO THEREMAINING ONE OF R-Y, G-Y AND B-YSIGNALS, AND MEANS FOR COUPLING SAID FIRST, SECOND AND THIRD INPUTTERMINALS TO THE RESPECTIVELY APPROPRIATE OUTPUT CIRCUIT MEANS.